Stem cells and small lymphocytes of congenitally asplenic-athymic mice. Quantitative and autoradiographic results.

A new type of animal: Mice with congenital absence of both the spleen and the thymus (ASAT mice) have been investigated. Haemato- and lymphocytopoietic findings in these mice were compared to findings in cogenitally asplenic (AS), congenitally athymic (AT), and normal mice. Major findiings were: (1) Normal number of CFU-S in bone marrow of ASAT mice and presence of CFU-S in lymph nodes of these mice, (2) High numbers of theta-positive cells in the bone marrow of ASAT and AT mice, (3) Low numbers of bone marrow lymphocytes as well as thoracic duct lymphocytes in ASAT and AT mice, and (4) Comparable proliferative kinetics of small lymphocytes in all 4 groups of mice, an exception being a rapid appearance of newly-formed small lymphocytes in thoracic duct and lymph nodes of ASAT mice.